1. Field of the Invention
The present invention relates to a power tool, and particularly, to a power tool including a commutator motor.
2. Description of the Related Art
As power tools, such as a grinder, a power tool which is configured to have a two-pole commutator motor as a power source has conventionally been known. As shown in FIGS. 13 and 14, the two-pole commutator motor 1020 includes a stator 1025 and a rotor 1021. The stator 1025 includes a substantially cylindrical stator core 1026. An inner peripheral surface of the stator is formed with a stator slot, and a portion of a stator coil bundle 1027 is housed in the stator slot, and the stator coil bundle 1027 is wound around the stator core 1026. The stator coil bundle 1027 has coil end portions 1028 and 1029 which protrude in an axial direction from a magnetic end corresponding to an axial end of the stator core 1026, and electric current flows to the stator coil bundle 1027 when a power tool 1001 which drives the motor 1020 is operated.
The stator coil bundle 1027 generates heat and rises in temperature during driving of the motor 1020. Motor output is suppressed due to such motor temperature rise. For this reason, it is general that the rotor 1021 is provided with a fan 1012 which rotates integrally with the rotor 1021, and the coil end portions 1028 and 1029 are cooled by cooling wind by the fan 1012. As a configuration which improves the cooling efficiency of the stator coil bundles 1027, as shown in FIGS. 13 and 14, a configuration in which the coil end portions 1028 and 1029 are formed thinly substantially in a plate shape and are made to extend in the axial direction of the stator core 1026, thereby increasing cooling surface area, is conceivable. Additionally, a configuration in which the coil end portion is split into two pieces, and a space through which cooling wind is made to pass is formed between the split coil end portions, thereby increasing the cooling surface area of the coil end portion, is conceivable. Such a two-pole commutator motor is described in, for example, Japanese Patent No. 3687479.
However, in the two-pole commutator motor provided in the conventional power tool, the coil end portion is made to extend in the axial direction of the stator core. Therefore, a problem occurs that the dimensions of the power tool in the axial direction of the stator core increase. Additionally, a problem occurs that the processing for splitting the coil end portion into two pieces is difficult, and the cost for manufacturing the power tool increases.
An object of the invention is to provide a power tool which can prevent dimensions from increasing, raise the cooling efficiency in a coil end portion, and suppress an increase in manufacturing cost.